The present invention relates to a key switch for a keyboard which produces little friction force and effectively eliminates the formation of a vacuum during the operation of the key switch.
Various key switches have been disclosed for computer keyboards. FIGS. 4 and 5 show a structure of key switch according to the prior art. This structure of key switch comprises an open key base 1' made on the frame of a keyboard, a key body 2' movably received within the key base 1', a key cap 3' spaced above the key base 1' and coupled to the key body 2', and a rubber cone 4' mounted on the circuit of the keyboard and disposed below the key body 2'. The key cap 3' has triangular bottom rods 3A respectively extended from the bottom thereof in four corners. The key base 1' has four longitudinal grooves 1A of arched cross section in the four corners thereof on the inside. The key body 2' comprises four triangular mounting slots 2A at the top, which receive the four triangular bottom rods 3A of the key cap 3' respectively, a flat bottom wall 2C supported on the rubber cone 4' at the top, four longitudinal flanges 2D of arched cross section respectively raised from the outside wall thereof in the four corners and side-matched with the four longitudinal grooves 1A of the key base 1'. The longitudinal flanges 2D of the key body 2' have each a bottom end terminating in a respective hooked portion 2B, which stops below an inward top flange on the key base 1' to keep the key body 2' coupled to the key base 1' when the key cap 3' is not depressed. A key switch has drawbacks. Because the longitudinal flanges 2D are side-matched with the longitudinal grooves 1A through surface contact but not point contact, a great friction force will be produced when the key body 2' is moved relative to the key base 1', and therefore the movement of the key body 2' will be affected. Because the top of the rubber cone 4' is closely attached to the flat bottom 2C of the key body 2', a vacuum will be produced upon each stroke of the key cap 3', causing the upward stroke of the key body 2' to be hindered. Furthermore, the design of the triangular slots 2A and longitudinal flanges 2D with hooked portions 2B complicates the injection molding process of the key body 2', causing the manufacturing cost of the key switch to be relatively increased.